Vibration-compensated inductive pickoff

ABSTRACT

1. An inductive pickoff of the character described comprising a stator having a plurality of pairs of spaced similar radially extending opposed pole pieces, spacing means by which the pole pieces of each pair of pole pieces are connected together adjacent one end thereof, a plurality of induction coils, one of said coils being mounted on one pole piece of each pair of pole pieces, and a rotor concentrically mounted with respect to said stator with arcuate sections thereof disposed between the opposed pole pieces of each pair of pole pieces.

United States Patent [191 Shapiro [111 3,803,566 [451 Apr. 9, 1974 VIBRATlON-COMPENSATED INDUCTIVE PICKOFF lnventor: PaulB. Shapiro, Dallas, Tex.

Assignee: Sperry Rand Corporation, Ford Instrument Company Division,

Wilmington, Del.

Filed: Mar. 3,- 1960 Appl. No.: 12,646

US. Cl 340/199, 336/45, 324/146, 340/196 Int. Cl G08c 19/16 Field of Search 340/194, 196, 199; 336/45; 324/146 References Cited UNITED STATES PATENTS 7/l940 Garlick, Jr. 340/196 2,929,053 3/1960 Bolton 340/l95 Primary Examiner-Maynard R. Wilbur Assistant Examiner-S. C. Buczinzki Attorney, Agent, or Firm-Samuel C. Yeaton; Howard P. Terry EXEMPLARY CLAIM 1. An inductive pickoff of the character described comprising a stator having a plurality of pairs of spaced similar radially extending opposed pole pieces, spacing means by which the pole pieces of each pair of pole pieces are connected together adjacent one end thereof, a plurality of induction coils, one of said coils being mounted on one pole piece of each pair of pole pieces, and a rotor concentrically mounted with respect to said stator with arcuate sections thereof disposed between the opposed pole pieces of each pair of pole pieces.

14 Claims, 18 Drawing Figures "ATENTEUAPR 9 m4 SHEET 1 0F &

V}//////7Y% Z7 INVENTOR PAUL 5. SHAP/RO ATTORNEYS PATENTEDAPR 91914 3803566 SHEEF 2 BF INVENTOR PA UL B. JHA P/EO ATTORNEYS VIBRATION-COMPENSATEI) INDUCTIVIE PllCIfiOlFF The invention herein described was made in the course of or under a contract or subcontract thereunder with the Department of the Army.

This invention relates to inductive pickoffs of the type which are adapted to actuate a voltage receiving mechanism in accordance with the angular change in the position of a shaft to which the pickoff is operatively connected.

Inductive pickoffs of this type generally comprise a stator having a plurality of radially disposed poles spaced 90 apart, each of which has an inductive winding mounted thereon to which a fixed input voltage is constantly applied. A concentrically arranged rotor coacts with the end faces of the poles to produce an output voltage from the coils which varies in accordance with, the relative position of the rotor with respect to the end faces of the poles. The output voltage is imparted to a receiver which is adapted to be actuated in accordance with fluctuation in the output voltage due to change in the angular position of a shaft to which the rotor is operatively connected. The receiver may be a dial which indicates the change in the angular position of the shaft, or a computer, or any of various other mechanisms which are responsive to change in the angular position of a shaft. I

Prior known inductive pickoffs of this character are all inherently sensitive to linear displacements of the rotor with respect to the stator which may be due to vibrations in the mounting for the pickoff. Any such change in the relative positions of the rotor and stator, due to linear displacement of the rotor, will materially change the output voltage which will create an error in the receiver with respect to the angular position of the rotor and the shaft to whichit is connected.

It is therefore the principal object of the present inventionto provide an inductive pickoff, for an angular position indicator, that is so constructed and arranged that it is not sensitive to vibrations in any plane.

Another object of the invention is to provide a pickoff of the aforesaid character in which all error due to linear displacement of the rotor in any direction is substantially, if not completely, eliminated.

More specifically, it is an object of the invention to provide an inductive pickoff of the aforesaid character which is so constructed and arranged that all linear displacement of the rotor in any direction due to vibration is automatically compensated for, whereby the voltage output thereof is maintained substantially constant for any given angular position of the rotor with respect to the stator.. I, g

To this end I'provide a stator of magnetic material which is adapted to be secured in fixed position and a concentrically disposed rotor of magnetic material which is adapted to be secured to a shaft, the varying angular positions of which are to be recorded.

The stator comprises two similar vertically spaced members, with a spacer therebetween, which are all securely bolted together. Each member comprises a ring having four inwardly extending radially disposed pole pieces spaced 90 apart. The spacer is the same size and shape as the upper and lower member without the pole pieces. An induction coil is wound'on each pole piece of the upper member adjacent the outer ends thereof.

2 The width of a wound coil is less than the length of a pole piece, so that a substantial portion of each pole piece is disposed inwardly of the coil thereon.

The rotor comprises a circular disk having two integral diametrically opposed arcuate sections, of 90 each, disposed about the periphery of the disk, the thickness of which sections is greater than the thickness of the disk. The rotor is concentrically mounted within the stator between the upper and lower members thereof with the arcuate sections thereof disposed midway between the pairs of vertically aligned pole pieces.

A constant input voltage is applied to the coils, and the induced output voltage thereof, which varies in accordance with the relative positions of the arcuate sections of the rotor with respect to the stator pole pieces, is imparted to a receiver. As previously stated the receiver maybe a graduated dial, an integrator, a corn puter or any other voltage receiver which is adapted to be electrically actuated in accordance with the angular position of the shaft upon which the rotor is mounted.

Having stated the principal objects of the inventionother and more specific objects of the invention will be apparent from the following specification and the accompanying drawings forming a part thereof in which: FIG. I is a plan view of an inductive pickoff, for an angular position indicator, constructed according to my invention:

FIG. 2 is a vertical section taken on the line 2-2 on .FIG. I;

the voltage source and to the receiver diagrammatically shown thereon;

I FIG. 7 is a vertical section taken on the line 7--7 on FIG. 6;

FIG. 6 is a plan view of the spacer, on the same scale as FIG. 6;

FIG. 9 is a vertical section taken on the line 99 on FIG. 8;

FIG. It) is a view similar to FIG. 11 showing a modified form of the invention;

FIG. II is a vertical section taken on the line II-II on FIG. It);

FIG. 12 is a plan view of the rotor used in the form of the invention shown in FIGS. I0 and II;

FIG. I3 is a vertical section taken on the line Iii-I3 onFIG. I2; I

FIG. 114 is a vertical section taken on the line I4-I4 on FIG. I2;

FIG. 15 is a plan view, on a slightly reduced scale, of one of the two similar vertically spaced stator elements shown on FIGS. III and II;

FIG. I6 is a vertical section taken on the line I6-I6 on FIG. I5;

FIG. I7 is a plan view, on the same scale of of the spacer shown on FIG. II; and

FIG. I8 is a vertical section taken on the line lib-J6 on FIG. I7.

The presently preferred form of the invention, as shown in FIGS. I to 9 inclusive of the drawings, will now be described in detail with the use of reference FIG. I5,

characters applied to the drawings. As shown therein the pickoff comprises a stator generally indicated by the numberal 1, and a rotor generally indicated by the numeral 2. The stator 1 comprises two similar vertically spaced elements 3 and 4 and a spacer 5 which are all secured tightly together by bolts 6, which extend through aligned apertures 7 in the elements 3, 4 and 8 in the spacer 5, and are provided with nuts 9. Each of the upper and lower similar elements 3 and 4 comprises an annular ring 10, of magnetic material, and four radially disposed equally spaced similar pole pieces 11, 12, 13 and 14 which are integral with the ring 10 and extend inwardly therefrom. When assembled as shown in FIGS. 1 and 2, the pole pieces 11 to 14 of the upper element 3 align with the pole pieces 11 to 14 respectively, of the lower element 4. The spacer 5 shown in detail in FIGS. 8 and 9 is the same shape and size as the upper and lower elements 3 and 4 minus the pole pieces 11 to 14.

Each of the pole pieces 1 1 to 14 of the upper element 3 has a similar induction coil mounted thereon which coils are designated 15, 16, 17 and 18 with the coil 15 being mounted upon the pole piece 11, the coil 16 being mounted upon the pole piece 12, the coil 17 being mounted upon the pole piece 13, and the coil 18 being mounted upon the pole piece 14. The coils are all connected together to form a bridge circuit. As shown in FIG. 6 the coils 15 and 16 mounted on the pole pieces 11 and 12 respectively, are wound counterclockwise, and the coils 17 and 18 mounted upon the pole pieces 13arid 14 respectively, are wound clockwise. A constant input voltage is applied to the coils 15 to 18 byiconductor means 19, and the varying output voltage of the coils is imparted to a receiver 20 by conductor means 21. The coils 15 to 18 are all mounted upon the pole pieces 11 to 14 closely adjacent the ring 10, by which the pole pieces are carried, and the width of the coils is considerably less than the length of the pole pieces so that the free ends of thepole pieces are disposed inwardly beyond the coils a substantial distance thereby providing a gap 22 between the opposed faces of each pair of vertically aligned pole pieces.

The rotor 2 comprises a circular hub disk 25, of magnetic material, having two integral diametrically opposed similar arcuate sections 26 and 27 of 90 each .disposed about the periphery of the disk. The thickness or depth of the sections 26 and 27 is substantially greater than the thickness of I the disk 25 and the mounting thereof is such that the sections 26 and 27 extend above and below the disk 25 with a 90 gap between opposing ends of the sections. The disk 25 is provided with a central aperture 28 for mounting upon a shaft 29 the angular position of which is to be indicated.

'In use the rotor 2 is concentrically mounted within the stator 1 intermediate the upper and lower elements 3 and 4 as shown in FIGS. 1 and 2. In FIG. 1 the rotor is shown in initial null position with one end of the arcuate section 26 disposed in the gap 22 between the pole pieces 11 and the other end thereof-disposed in the gap 22 between the pole pieces 12, and with one end of the arcuate section 27 disposed in the gap 22 between the pole pieces 13 andthe other end thereof disposed in the gap 22 between the pole pieces-14. Any angular change in the relative position of the rotor and stator with respect to each other will change the volume of the gaps 22 and thereby increase or decrease the flux path, which will correspondingly change the magnetomotive energy of the gaps, which in turn will change the output voltage of the coils which is a function of the magnetomotive energy of the gaps. If the rotor is rotated clockwise from the null position shown in FIG. 1 the volume of the gaps 22 between the pole pieces 12 and between the pole pieces 14 will be decreased, and the volume of the gaps 22 between the pole pieces 11 and between the pole pieces 13 will be correspondingly increased. This will induce an output voltage in one direction the value of which will be dependent on the distance the rotor is moved out of initial null position. If the rotor is rotated counterclockwise from the null position shown in FIG. 1 the volume of the gaps 22 between the pole pieces 12 and between the pole pieces 14 will be increased and the volume of the gaps 22 between the pole pieces 11 and between the pole pieces 13 will be correspondingly decreased, which induce an output voltage in the opposite direction, the value of which will likewise be dependent upon the distance the rotor is moved out of null position.

From FIG. 1 it will be apparent that if the rotor 2 is rotated approximately 15 clockwise from the null position shown in FIG. 1, the volume of the gaps 22 between the pole pieces 12 and between the pole pieces 14 will be decreased to a minimum, and the volume of the gaps 22 between the pole pieces 11 and the pole pieces 13 will be increased to a maximum, and that any further rotation of the rotor in a clockwise direction will have no further effect on the voltage output of the coils. The reverse is true if the rotor 2 is rotated approximately 15 in a counterclockwise direction. It will therefore be seen that the inductive pickoff as illustrated herein is operative to indicate the change in angular position of the shaft 29 within a range between 15 and 15 with respect to the null position thereof. It will further be apparent that this range will be increased by increasing the width of the various pole pieces and decreased by decreasing the width of the pole pieces.

The construction and arrangement of the stator l and rotor 2 are such that any linear movement, in any direction, of the rotor with respect to the stator will not essentially create a change in the total area and length of the gaps 22 and consequently the flux paths. The output voltage will therefore remain constant for any given angular position of the rotor with respect to the stator. From FIG. 2 it will be apparent that any vertical movement of the rotor between the upper and lower pole pieces will not change the volume of the gaps. If the rotor is moved linearly to the right or left from the position shown in FIG. 1 the volume of the gaps 22 between the pole pieces 11 and between the pole pieces 13 will not be changed. If the movement is to the right the volume of the gap 22 between the pole pieces 12 will be decreased, and the volume of the gap 22 between the pole pieces 14 will be correspondingly increased; and if the movement is to the left the volume of the gap 22 between the pole pieces 12 will be increased and the volume of the gap 22 between the pole pieces 14 will be correspondingly decreased. The increase in volume between one pair of pole pieces will therefore be compensated for by the decrease in volume between the opposed pair of pole pieces.

Since a change in gap volume between a pair of pole pieces increases or decreases the flux path it will be apparent from the foregoing that an increase in the flux path between one pair of pole pieces will be compensated for by a corresponding decrease in the flux path between the opposing pair of pole pieces and that therefor the output voltage from the pickoff to the receiver will not be affected by any relative linear movement between the stator and rotor.

The modified form of the invention, as shown in FIGS. to 18 of the drawing, will now be described in detail. As shown therein this modified form of pickoff comprises a stator 31 and a rotor 32. The stator 31 comprises two similar vertically spaced elements 33 and 34 and an interposed spacer 35 which are all secured together by bolts 34, which extend through aligned apertures 37 in the elements 33 and 34 and 38 in the spacer 35, and are provided with nuts 39. Each of the upper and lower similar elements 33 and 34 comprises a ring 40, of magnetic material, and four equally spaced pole pieces 41, 42, 43 and 44 which are integral with the ring 41) and extend radially outwardly therefrom. When assembled as shown in FIGS. 10 and 11 the pole pieces 41 to 44 of the upper element 33 vertically align with the pole pieces 41 and 44 respectively, of the lower element 34. The spacer 35 shown in detail in FIGS. 17 and 18 is the same shape and size as the upper and lower elements 33 and 34 minus the pole pieces 41 to 44. I

- Each of the pole pieces 41 to 44 of the upper element 33 has a similar induction coil mounted thereon which coils are designated 45, 46, 47 and 43, with the coil 45 being mounted upon the pole piece 41, the coil 46 being mounted on the pole piece 42, and the coil 47 being mounted on the pole piece 43, and the coil 48 being mounted on the pole piece 44. The coils 45 to 43 are wound upon the pole pieces 41 to 44 and connected together to form a bridge'circuit in the same manner that the coils to 13 are connected together and wound upon the pole pieces 11 to 14 of the form of the invention shown in FIGS. 1 to 9.

The coils 45 to 44 are all mounted upon the pole pieces 41 to 44 closely adjacent the ring 411, with which the pole pieces 41 to 44 are integral, and the width of the coils 45 to 48 is considerably less than the length of the pole pieces 41 to 44 so that the free ends of the pole pieces 41 to 44 are disposed outwardly beyond the coils 45 to 48 a substantial distance thereby providing a gap 52 between the opposed faces of each pair of vertically aligned pole pieces 41 to 44.

The rotor 32 comprises-a hub 55 to which two diametrically opposed magnetic material sections Stiand 57'of 90 each are connected by arms 53. The mounting of the rotor 32, with respect to the stator 51, is such that one end of the section 56 is disposed between the pole pieces 41 and the other end thereof is disposed between the pole pieces 42, and that one end of the section 57 is disposed between the pole pieces 43 and with the other end thereof disposed between the pole pieces 44. The hub 55 is provided with an aperture 59 for mounting the rotor 32 upon a shaft 61), the angular position of which is to be indicated.

The operation of this form of the invention, due to any relative linear movement between the stator 31 and the rotor 32 is the same as that explained in connection with the form of the invention shown and described in connection with the form of the invention shown in FIGS. 1 to 9.

From the foregoing it will be apparent to those skilled in this art that I have provided a very simple and efficient mechanism for accomplishing the objects of the invention.

It is to be understood that I am not limited to the forms of the invention shown and described herein as various modifications may be made therein within the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. An inductive pickoff of the character described comprising a stator having a plurality of pairs of spaced similar radially extending opposed pole pieces, spacing means by which the pole pieces of each pair of pole pieces are connected together adjacent one end thereof, a plurality of induction coils, one of said coils being mounted onone pole piece of each pair of pole pieces, and a rotor concentrically mounted with respect to said stator with arcuate sections thereof disposed between the opposed pole pieces of each pair of pole pieces.

2. An inductive pickoff of the character described having a stator and a concentrically mounted rotor in which said stator comprises; a pair of spaced aligned members, a connecting spacing means therebetween, each of said members having a plurality of radially extending pole pieces, the pole pieces of one of said members being disposed in opposed alignment with the pole pieces of the other of said members, a plurality of inductive coils, one of said coils being mounted upon each pole piece of one of said members, and in which said rotor is provided with arcuate sections which are disposed between opposed pole pieces of said members.

3. An inductive pickoff of the character described having a stator and a concentrically mounted rotor in which said stator comprises; a pair of spaced annular members, an annular spacing means disposed between said members, means by which said members and said spacing means are secured together in alignment, each of said annular members being provided with four similar equally spaced radially extending pole pieces thereby providing four pair of spaced opposed pole pieces with a gap therebetween, a plurality of similar induction coils one of which is mounted upon each pole piece of one of said members, and in which said rotor comprises a hub having two diametrically opposed con centric arcuate sections of each secured thereto, said arcuate sections being disposed in the gaps between opposed pole pieces of each pair of pole pieces.

4. An inductive pickoff of the character described having a stator means and concentrically mounted rotor means in which said stator means comprises; four similar pair of concentric radially extending equally spaced pole pieces, each pair of pole pieces comprising two spaced opposed similar pole pieces which are connected together at one end thereof with a spacing means interposed therebetween thereby providing a gap therebetween, mounting means by which said pairs of pole pieces are secured in fixed position with respect to each other, a plurality of similar induction coils one of which is mounted upon one pole piece of each pair of pole pieces, and in which said rotor is provided with arcuate sections which are disposed in the said gaps be tween the pole pieces of each pair of pole pieces.

5. An inductive pickoff as defined by claim 1 in which said spacing means is common to all of said plurality of pairs of pole pieces.

6. An inductive pickoff as defined by claim 2 in which the said pole pieces of said members extend radially inward from said members, and in which said arcuate sections are disposed within said stator.

7. An inductive pickoff as defined by claim 2 in which the said pole pieces of said members extend radially outward from said members and in which said arcuate sections are disposed outwardly of said stator.

8. An inductive pickoff as defined by claim 3 in which the said pole pieces of said annular members extend redially inward from said annular members, and in which said arcuate sections are disposed within said annular spacing means. 9. An inductive pickoff as defined by claim 3 in which the said pole pieces of said annular members extend radially outward from said annular members, and in which said arcuate sections are disposed in said gaps outwardly of said annular spacing means.

10. An inductive pickoff as defined by claim 4 in which the pole pieces of each pair of pole pieces extend radially inwardly from the connected ends thereof, and in' which said arcuate sections are disposed within said stator means.

11. An inductive pickoff as defined by claim 4 in which the pole pieces of each pair of pole pieces extend radially outwardly from the connected ends thereof, and in which said arcuate sections are disposed outwardly of said stator means.

12. An inductive pickoff of the character described comprising, a stator having a plurality of pairs of spaced similar radially extending opposed pole pieces, spacing means by which the pole pieces of each pair of pole pieces are connected together adjacent one end thereof, voltage inducing means operatively associated with said plurality of pairs of pole pieces, said voltage inducing means being operative to induce a voltage in said pole pieces, sensing means operatively associated with said voltage inducing means, said sensing means being operative to detect a change in voltage in said pole pieces and to impart a corresponding signal to a receiver, and a rotor concentrically mounted with respect to said stator with arcuate sections thereof disposed between the opposed pole pieces of each pair of pole pieces.

13. An inductive pickoff as defined by claim 12 in which said voltage inducing means comprises a plurality of similar induction coils one of which is mounted upon one pole piece of each pair of pole pieces.

14. An inductive pickoff as defined by claim 13 in which said sensing means comprises a bridge circuit into which said plurality of coils are connected. 

1. An inductive pickoff of the character described comprising a stator having a plurality of pairs of spaced similar radially extending opposed pole pieces, spacing means by which the pole pieces of each pair of pole pieces are connected together adjacent one end thereof, a plurality of induction coils, one of said coils being mounted on one pole piece of each pair of pole pieces, and a rotor concentrically mounted with respect to said stator with arcuate sections thereof disposed between the opposed pole pieces of each pair of pole pieces.
 2. An inductive pickoff of the character described having a stator and a concentrically mounted rotor in which said stator comprises; a pair of spaced aligned members, a connecting spacing means therebetween, each of said members having a plurality of radially extending pole pieces, the pole pieces of one of said members being disposed in opposed alignment with the pole pieces of the other of said members, a plurality of inductive coils, one of said coils being mounted upon each pole piece of one of said members, and in which said rotor is provided with arcuate sections which are disposed between opposed pole pieces of said members.
 3. An inductive pickoff of the character described having a stator and a concentrically mounted rotor in which said stator comprises; a pair of spaced annular members, an annular spacing means disposed between said members, means by which said members and said spacing means are secured together in alignment, each of said annular members being provided with four similar equally spaced radially extending pole pieces thereby providing four pair of spaced opposed pole pieces with a gap therebetween, a plurality of similar inductioN coils one of which is mounted upon each pole piece of one of said members, and in which said rotor comprises a hub having two diametrically opposed concentric arcuate sections of 90* each secured thereto, said arcuate sections being disposed in the gaps between opposed pole pieces of each pair of pole pieces.
 4. An inductive pickoff of the character described having a stator means and concentrically mounted rotor means in which said stator means comprises; four similar pair of concentric radially extending equally spaced pole pieces, each pair of pole pieces comprising two spaced opposed similar pole pieces which are connected together at one end thereof with a spacing means interposed therebetween thereby providing a gap therebetween, mounting means by which said pairs of pole pieces are secured in fixed position with respect to each other, a plurality of similar induction coils one of which is mounted upon one pole piece of each pair of pole pieces, and in which said rotor is provided with arcuate sections which are disposed in the said gaps between the pole pieces of each pair of pole pieces.
 5. An inductive pickoff as defined by claim 1 in which said spacing means is common to all of said plurality of pairs of pole pieces.
 6. An inductive pickoff as defined by claim 2 in which the said pole pieces of said members extend radially inward from said members, and in which said arcuate sections are disposed within said stator.
 7. An inductive pickoff as defined by claim 2 in which the said pole pieces of said members extend radially outward from said members and in which said arcuate sections are disposed outwardly of said stator.
 8. An inductive pickoff as defined by claim 3 in which the said pole pieces of said annular members extend redially inward from said annular members, and in which said arcuate sections are disposed within said annular spacing means.
 9. An inductive pickoff as defined by claim 3 in which the said pole pieces of said annular members extend radially outward from said annular members, and in which said arcuate sections are disposed in said gaps outwardly of said annular spacing means.
 10. An inductive pickoff as defined by claim 4 in which the pole pieces of each pair of pole pieces extend radially inwardly from the connected ends thereof, and in which said arcuate sections are disposed within said stator means.
 11. An inductive pickoff as defined by claim 4 in which the pole pieces of each pair of pole pieces extend radially outwardly from the connected ends thereof, and in which said arcuate sections are disposed outwardly of said stator means.
 12. An inductive pickoff of the character described comprising, a stator having a plurality of pairs of spaced similar radially extending opposed pole pieces, spacing means by which the pole pieces of each pair of pole pieces are connected together adjacent one end thereof, voltage inducing means operatively associated with said plurality of pairs of pole pieces, said voltage inducing means being operative to induce a voltage in said pole pieces, sensing means operatively associated with said voltage inducing means, said sensing means being operative to detect a change in voltage in said pole pieces and to impart a corresponding signal to a receiver, and a rotor concentrically mounted with respect to said stator with arcuate sections thereof disposed between the opposed pole pieces of each pair of pole pieces.
 13. An inductive pickoff as defined by claim 12 in which said voltage inducing means comprises a plurality of similar induction coils one of which is mounted upon one pole piece of each pair of pole pieces.
 14. An inductive pickoff as defined by claim 13 in which said sensing means comprises a bridge circuit into which said plurality of coils are connected. 